1. Field of Invention
This invention relates to an all-optical label swapping system and swapping method, and more particularly to an all-optical label swapping system and swapping method using a superimposed ASK label.
2. Related Art
Dense-wavelength-division-multiplexing (DWDM) transmission and generalized multi-protocol label switching (GMPLS) are considered the key enabling technologies for the next generation optical Internet backbone. In a GMPLS-based optical switch/router, the low-speed label associated with a high-speed payload is extracted, processed, and replaced at every intermediate network switching node. Meanwhile, the high-speed payload is optically switched and controlled by the electrically processed label to an appropriate output fiber as an entirely untouched entity. Therefore, a GMPLS-based optical switch/router is transparent to various payload data rates, 10 Gbps, 40 Gbps, etc., and formats, SONET, Gigabit, etc., and can use economically realizable processors for the low-speed labels, e.g., a Fast Ethernet.
Many optical label swapping techniques have been proposed. Among them, the time-domain multiplexing technique requires extremely precise control of timing and alignment. The subcarrier multiplexed labeling technique requires extra bandwidth beyond traditional baseband payload, and requires stringent wavelength accuracy and stability if a fixed optical notch filter, e.g., a fiber Bragg grating, is used to erase the old label. The orthogonal modulation technique, including ASK/FSK and ASK/DPSK, exhibits severe transmission system penalty due to its inherently low extinction ratio of high-speed payload signals.